THE PHOTODISSOCIATION OF OClO: PATHWAYS OF CHLORINE ATOM PRODUCTION.

Abstract

The photodissociation mechanism of the $ClO_{2}$ radical which gives rise to chlorine atoms has been investigated using large scale internally contracted multireference configuration interaction wave functions. Potential energy surfaces of the OClO isomer have been calculated for the process: $OClO (X^{2}B_{1}, ^{2}B_{2}, ^{2}A_{1}, A^{2}A_{2}) \to, Cl (^{2}P) + O_{2} (X^{3} \Sigma_{g}{^{\,-}},a^{1} \Delta_{g})$ The lowest energy pathway is calculated to occur via the $^{2}B_{2}(^{2}A)$ potential energy surface with a barrier of less than I eV. The structure of the transition state is only slightly distorted from $C_{2v}$ symmetry, which is in excellent agreement with the recent experiments of Davis and $Lee.^{1}$ Competition between this chlorine-producing channel and the dominant one, $OClO to ClO (X^{2}\Pi) + O (^{3}P)$, results in the strong vibrational mode specificity also observed experimentally. Additionally, these calculations indicate that the branching ratio for production of $X^{3} \Sigma_{g}{^{\,-}}$ and $a^{1}\Delta_{g}O_{2}$ is dictated by the intersection of the $^{2}B_{2}$ and $^{2}A_{1}$ surfaces, which occurs at geometries close to the transition state. $^{1}$ H.F. Davis and Y.T. Lee. J. Phys. Chem. 96, 5681 (1992).